Regional averages blur the unequal distribution of wealth — and the tax families would pay — in a vast territory of 2.9 million people in King, Snohomish and Pierce counties. The average Eastside house sold for $746,500 in June, while Pierce Transit says 44 percent of its riders subsist on less than $20,000 a year.

The No on ST3 campaign has already published its own calculator, and a message that “all these taxes will NEVER solve our traffic problems.”

Sound Transit says it will also create a tax calculator soon.

The $54 billion fall ballot measure features light-rail extensions reaching as far as Everett, South Kirkland, Issaquah, Tacoma, West Seattle and Ballard, as well as added South End commuter-train capacity, and bus rapid transit in the Interstate 405 and Highway 522 corridors.

Pro-ST3 campaigners at Mass Transit Now say high-capacity transit will allow commuters to cut driving costs and escape road congestion that currently wastes an average 63?hours per year.

For years, poorer people have paid a greater fraction of their wealth than rich people toward transit sales taxes, aggravating the state’s regressive tax system. Besides more sales tax, ST3 would also raise car-tab taxes, considered progressive because they fall hardest on owners of new and luxury cars.

Rising property taxes mostly track with wealth, but they can also squeeze homeowners of modest means, if they bought homes in a cheaper era.

Here is a tour of the taxes being proposed.

Property tax

The introductory property-tax rate would be $25 per $100,000 of home value.

And during the two years while officials towed their package through the Legislature and onto the ballot, King County home values gained 24 percent on average.

From a pro-rail perspective, those gains create a higher launchpad for ST3’s property-tax income, compared with a flat housing market.

To calculate your ST3 property tax, find your 2016 home value on the value cards that county assessors are mailing this summer, for property-tax year 2017, and do the math. Commercial- property owners would be billed as well.

Chances are, you’re now wondering if transit property taxes would skyrocket after 2017, presuming home values continue their rapid rise.

So the average ST3 property-tax bill would increase 1?percent in 2018 and beyond. As a rate, the initial $25 would gradually decrease, if values rise.

It’s hard to know how much tax that landlords would pass through to renters or business tenants. That would vary. For the sake of its household estimates, Sound Transit assumes apartment dwellers would shoulder the whole increase.

Recent spikes in house values don’t change the numbers much, because Sound Transit previously cited 2015 Zillow figures that turned out to be nearly identical to the 2016 official assessed values. When transit staff did a new analysis, with the official values, that made only a small difference in median taxes.

Sales tax

The sales tax would increase half a percentage point, or a nickel per $10 purchase.

It is the most elusive tax to estimate, because few people keep all their purchase receipts.

And the total changes every year — depending on whether you settle for ordinary stuff like beer, shoes and video games, or splurge on a refrigerator, a bathroom remodel or new vehicle.

Currently, a working-poor household making $45,000 to $55,000 a year spends an average $1,988 for sales tax, while a household making $105,000 to $140,000 spends $3,832, according to the state Department of Revenue. (That’s based on a 9 percent statewide tax average, actually a half-cent below most of urban Puget Sound.)

If that seems high, these state figures indeed far exceed what’s spit out by the federal IRS deduction calculator, because the feds ignore your sporadic major purchases, unless you report those.

If another half a percentage point is added, that boosts the tax $111 annually for our working-poor household and $214 for the upscale household, the state model shows.

ST3 sales taxes would be in addition to the 0.9 percent the agency already collects, as well as other sales taxes you pay for local bus services.

Car-tab tax

Sound Transit now charges 0.3 percent, or $30 per $10,000 of vehicle value, in car-tab taxes until that tax expires in 2028.

ST3 would tack on a permanent $80 per $10,000 in value, bringing the total rate to $110.

To complicate matters, the official “value” for tax purposes is usually higher than what you might get by selling your car, or find in the Kelley Blue Book. Your car depreciates faster in real life than it does in the Legislature. That disparity is a vestige of the 1990s, when the state inflated its car-depreciation charts to rake in more dollars for ferries and revenue sharing with bus agencies, cities and counties.

Finding your proposed ST3 car tax is easy. Take your 2016 car-tab bill and locate the figure for the “RTA Tax,” which was approved in 1996. Multiply it by 2.67 to determine the effect of raising a $30 tax rate by $80. To refine that figure further, multiply it by 0.93, since your official car value would depreciate 7?percent by 2017.

After it initially projected an average car value of $10,135 in King, Snohomish and Pierce counties, further research found the median value was only $5,333. In other words, a minority of people own new or luxury cars that drive up the average, while the masses own older wheels.

That recalculation means most car owners would pay less than previous Sound Transit examples suggested.

Bottom line

If it’s any consolation, the new analysis in car values dropped Sound Transit’s total tax increase for a typical household to $326 next year, instead of the $392 cited last winter.

When performing tax math, it’s worth recalling the Oscar Wilde proverb — a cynic is a man who knows the price of everything and the value of nothing.

“The bigger argument here is the cost of car ownership, of $10,000 a year,” said ST3 supporter Shefali Ranganathan, executive director of the Transportation Choices Coalition. “If you have the ability to go from a two-car household to a one-car household, is that progressive for you?”

The American Public Transportation Association estimates a Seattle-area family would save $11,040 yearly by dropping a car and using transit.

That’s a huge benefit, though the region’s eight rail branches would still miss several communities that pay the taxes, including Renton, Bothell, White Center, Burien and Sammamish.

Bellevue City Councilmember Kevin Wallace, an ST3 opponent, said voters deserve a calculator to grasp what the unprecedented $54?billion proposal means to their family budgets, for service that won’t arrive for two decades and won’t cure congestion.

“It’s just a good educational tool, and people need to appreciate how much they and their neighbors will pay every year for light-rail extensions,” he said.